This invention relates to fluorescence detection, and more particularly, to a system capable of increased dynamic range and four-color detection.
Fluorescence readers are often used for re-sequencing or gene expression studies. In these systems, light such as that from a laser is directed onto a target, which may include molecules capable of fluorescing. Of course, the light could come from the process of chemi-luminescence as well. The emitted fluorescent light is then detected and analyzed. Oftentimes, multiple color dyes are utilized. For example, four colors may be used. The light is detected by florescence detection devices such as confocal scanning microscopes and imagers that utilize detection elements such as photomultiplier tubes (PMTs), avalanche photo-diodes (APDs), and charge-coupled devices (CCDs).
Different users, or the same user performing different experiments, may require different operating modes of the detection equipment. If a particular slide employs four color dyes, then four separate detectors can be used to detect each of the four colors. If, however, there are only two dyes on a slide, the experimenter may wish increased dynamic range in the output with respect to the two dyes. Heretofore, two separate instruments would be required in order both to detect four separate colors or to detect two colors with a higher dynamic range. Alternatively, multiple scans would have had to be used with, for example, a two-color/two-detector instrument. See, U.S. Pat. No. 6,078,390. The present invention is directed to a single versatile instrument that can operate selectively in these two modes.